Poland's political geography has often been the topic of excited - if at times rather overheated - comment, much of which tends to focus on the correspondence between the lines along which Poland was partitioned and voting patterns in the present day. The legacies of partition - and related legacies of economic and institutional development and cultural consolidation (or de-consolidation) - have clearly played a role in influencing electoral choices, although the definitive article that parses the various strands of correlation and causation remains to be written.

Some of the folk wisdoms about Poland's electoral geography continue to outlast their empirical falsification, but we can say two things for sure:

PiS and PO have tended to be more successful in different areas.

At the 2015 election, PiS made significant inroads into former PO strongholds (which turned out not to be so strongly held).

Assuming as I do - in the absence of better information - that the geographical distribution of votes in the 2015 election still remains a relevant variable for understanding how national polling results translate into seat shares, current regional strengths look something like the following.

PiS's stronghold is in the east and south. In the Rzeszów constituency, PiS would, on current polling, have 12 of the 15 seats available (note that the shading of the plots corresponds not to the individual district magnitudes, but to the gradient from 0 to 20, which is the largest district magnitude, in the Warsaw metropolitan constituency). By contrast, in Gdynia, which has a district magnitude of 14, PiS would have only 5 seats.

Support for PO has tended to be more evident in the west and north, and in major cities. The map roughly captures this, although the differences are not as stark as in previous years, and in any case this starkness was often a product of the colour-coding strategies of newspapers' graphic designers, who have an understandably limited tolerance for shades of grey.

Instead of the clash-of-the-primary-colours maps we tend to see in newspaper articles and memes, a better way to get a handle on the current state of play in Poland's electoral geography is to look at the absolute differences between projected seat shares for PiS and PO. The map below is based on a colour coding that runs from orange (PO have all the available seats) through white (PO and PiS have an even number of seats) to dark blue (PiS have all the available seats). The numbers correspond to the extent of the advantage enjoyed by the party which is ahead in that constituency.

As the map shows, PiS's dominance is evident in the fact that it clearly outdoes PO in its own strongholds, while restricting PO to only a couple of constituencies in which it outperforms PiS (only in Poznań would PO's advantage over PiS exceed a single legislator). While there is clearly a geographical gradation to the electoral politics of Poland's Big Two parties, western Poland is far from terra incognita to PiS.

Maps for the minor parties are less revealing, partly because these parties do not necessarily have strong electoral profiles, but also because these maps show where parties gain seats, and not where they accumulate votes (which might give more of a clue about where these parties have the potential to be stronger, but that's a future blogpost).

The decline in support for Nowoczesna over the last couple of years is evident in the rather washed-out character of its electoral map, although in any case support for the party was not especially regionally concentrated in 2015. While Nowoczesna could still count on two seats in Warsaw and one in the surrounding commuter-belt 'doughnut', for the most part it would be picking up scraps after PO in western regions.

Support for Kukiz'15 is broadly dispersed, and this is reflected in the fact that it would - on a current 9% vote share - capture at least one seat in all but three constituencies, with Wałbrzych, Nowy Sącz and Poznań resistant to the party's charms, and Kielce and Opole - party leader Paweł Kukiz's home turf - more open to them, resulting in two seats apiece.

The heartland of PSL in central and eastern Poland is still in evidence, although on current polling it could hope for no more than a single seat in any given constituency.

In recent weeks, SLD has made something of a comeback in the polls. While its geographic appeal has been harder to pin down than that of PiS or PO, from the performance of the ill-fated United Left alliance in the 2015 elections we can conclude that it would do badly in the south-east of Poland (where it has generally tended to struggle), but pick up a handy couple of seats in Warsaw thanks to its enduring appeal among the substantial contingent of urban leftists who remain unconvinced by the parvenu Razem's long-term viability as an electoral option.